1-20号元素的原子序数、质子数、中子数、核外电子数、相对原子质量答:1,氢,H,Hydrogen,1.0079,气态,1,0,0,0,0,0,0,1s1,-259.14C,-252.87C 2,氦,He,Helium,4.0026,气态,2,0,0,0,0,0,0,1s2,-272C26ATM,-268.6C 3,锂,Li,Lithium,6.94,固态,2,1,0,0,0,0,0,2s1,180.54C,1347C 4,铍,Be,Beryllium,9.01218,固态,2,2,0,0,0,0,0...